The present invention relates to protective coatings for turbine engine components, such as aerospace components. In particular, the present invention relates to methods for forming coatings that provide oxidation resistance to turbine engine components.
A gas turbine engine typically consists of an inlet, a compressor, a combustor, a turbine, and an exhaust duct. The compressor draws in ambient air and increases its temperature and pressure. Fuel is added to the compressed air in the combustor, where it is burned to raise gas temperature, thereby imparting energy to the gas stream. To increase gas turbine engine efficiency, it is desirable to increase the temperature of the gas entering the turbine stages. This requires the first stage turbine engine components (e.g., vanes and blades) to be able to withstand the thermal and oxidation conditions of the high temperature combustion gas during the course of operation.
To protect turbine engine components from the extreme conditions, such components typically include metallic coatings (e.g., aluminide and MCrAlY coatings) that provide oxidation and/or corrosion resistance. The metallic coatings may also function as bond coats to adhere thermal barrier coatings to the substrates of the turbine engine components. Existing bond coats are applied to turbine engine components using a variety of deposition techniques (e.g., plasma spraying, cathodic arc, pack cementation, and chemical vapor deposition techniques). The ceramic thermal barrier coatings are then applied over the bond coats to thermally insulate the turbine engine component from the extreme operating conditions. However, over the course of operation, the thermal barrier coatings may be worn away (e.g., spalling and abrasive removals), thereby exposing the bond coats and the underlying substrates of the turbine engine components to the high operating temperatures. This exposure can eventually result in thermal degradation of the turbine engine component, which correspondingly may reduce operational efficiencies of the gas turbine engine.